1. Field of the Invention
The present invention relates to a semiconductor wafer pollutant measurement apparatus which is called an auto scanning system, in which the pollutant includes metal impurities, and more particularly, to a scan stage on which a wafer is loaded to then rotate in the case of scanning surface of the wafer in order to collect pollutants such as metal impurities.
2. Description of the Related Art
In general, as a semiconductor device is high-integrated, various kinds of pollutants that are produced in semiconductor manufacturing lines and semiconductor manufacturing processes are adsorbed on the surfaces of wafers. As a result, various kinds of pollutants that are adsorbed on the surfaces of wafers affect performance and yield of semiconductor devices.
Accordingly, an analysis of pollutants having sticked on the wafer surface has become important in manufacturing semiconductor devices. In the case of a conventional pollutant analysis method, a predetermined wafer is selected between the respective semiconductor manufacturing lines or the respective semiconductor manufacturing processes, and the surface of the selected wafer is scanned, to thus collect a sample of pollutants for analyzing the pollutants having sticked on the wafer surface, and analyze the collected pollutants sample using a destructive analysis method such as an atomic absorption spectroscopy and an inductively coupled plasma ICP-mass spectroscopy, and a nondestructive analysis method such as a total X-ray fluorescent analyzer.
That is, according to the conventional art, after the predetermined wafer has been selected between the respective semiconductor manufacturing lines or the respective semiconductor manufacturing processes, an oxide film that has been coated on the wafer surface should be removed before pollutants having sticked on the wafer surface are collected, in order to collect the pollutants accurately. This has been realized by a vapor phase decomposition (VPD) device.
The VPD device includes a process chamber in which a process proceeds, a loading plate which is positioned in the chamber and on which a wafer is loaded, and a container containing a hydrofluoric acid (HF) which decomposes an oxide film that is coated on the wafer surface. If a wafer is transferred on the loading plate which is installed in the process chamber, the wafer is safely placed in the process chamber for a given time. As a result, the oxide film that has been coated on the wafer surface is completely decomposed by vapor of the hydrofluoric acid (HF) which has been naturally evaporated from the hydrofluoric acid (HF) container.
Thereafter, a user takes out the wafer from the process chamber, and then drops a scanning solution on the wafer surface. The user scans the wafer surface directly manually, with the scanning solution, to thereby collect a sample of pollutants for pollution analysis of analyzing the pollutants having sticked on the wafer surface. Of course, the collected sample is analyzed to thereby measure a pollution level.
The Korean Patent Registration No. 10-0383264 entitled “Apparatus and method for collecting metallic impurity on a semiconductor wafer” corresponding to U.S. Patent Application Publication No. US 2002/0134406 A1 is already known as the semiconductor wafer pollutant measurement apparatus. The semiconductor wafer metallic impurity collecting apparatus generally includes a process chamber, a transfer unit, a loader unit, a vapor phase decomposition unit, a scanning unit, a drying unit, an unloader unit, and a center control unit that controls the semiconductor wafer metallic impurity collecting apparatus on the whole.
Here, the transfer unit, the loader unit, the vapor phase decomposition (VPD) unit, the scanning unit, the drying unit, and the unloader unit among the components of the semiconductor wafer metallic impurity collecting apparatus are implemented in the process chamber. That is, the transfer unit, the loader unit, the vapor phase decomposition unit, the scanning unit, the drying unit, and the unloader unit are placed in a semi-circular form where the transfer unit is placed at the center of the semi-circular form, and the loader unit and the unloader unit are placed at the start and end portion of the semi-circular form, respectively. Here, the vapor phase decomposition unit, the scanning unit, and the drying unit are sequentially installed between the loader unit and the unloader unit.
Among the accompanying drawings, FIG. 1 is a partially cutoff perspective view schematically showing the whole structure of a conventional semiconductor wafer pollutant measurement apparatus.
As illustrated in FIG. 1, if a predetermined wafer is selected to analyze a pollution level of the selected wafer at a semiconductor manufacturing line or process, a user transfers the selected wafer to a loader unit which is positioned in the process chamber of the semiconductor wafer pollutant measurement apparatus.
Thereafter, if the user tightly closes the process chamber and then makes the semiconductor wafer pollutant measurement apparatus operate, the transfer unit transfers the wafer located in the loader unit to the loading plate in the vapor phase decomposition (VPD) unit. Then, the vapor phase decomposition (VPD) unit tightly seals the wafer transferred to the loading plate and then decomposes an oxide film coated on the wafer surface using vapor of the hydrofluoric acid (HF).
Then, if the oxide film coated on the wafer surface has been completely decomposed, the transfer unit transfers the wafer located in the vapor phase decomposition (VPD) unit again to an align unit in the scanning device.
Thereafter, the wafer align unit aligns position of the transferred wafer accurately using an align hand, and simultaneously the scanning arm is rotated into the position of a nozzle tray. Accordingly, the nozzle provided in the nozzle tray is inserted into the scanning arm. Then, the scanning arm makes the nozzle inhale a predetermined amount of a scan solution from a scan solution bottle which is installed at the center of the nozzle tray, and then moves to the upper portion of the wafer, to thereafter approach the center of the wafer slowly.
Then, the scanning arm stops the approach when the center of the wafer substantially contacts the nozzle inserted into the scanning arm. If the approach of the scanning arm to the center of the wafer stops, a pump discharges part of the scan solution inhaled by the nozzle via a pumping fluid path of the scanning arm to the surface of the wafer, and makes the scan solution cohered in a droplet form between the lower portion of the nozzle and the wafer surface.
Thereafter, if the scan solution is cohered in a droplet form in the lower portion of the nozzle that has been inserted into the scanning arm and contacts the wafer surface, the wafer align unit makes the wafer rotate in one direction slowly, and the scanning arm makes the lower portion of the nozzle, that is, a portion where the scan solution contacts the wafer surface move slowly in one direction. Here, as the pollutants on the wafer surface contacts the externally exposed scan solution, they are of course absorbed into the scan solution.
Here, when the scanning arm moves once, a wafer takes a turn, and when the scanning arm moves once again, the wafer takes a turn again. That is, the wafer is scanned in a step-by-step style. As described above, if the scan solution is not seceded from the lower portion of the nozzle but scanning of a wafer is ended, the wafer align unit stops rotation and the scanning arm also stops movement. In this case, the pump inhales all the scan solution which has been used for scanning the wafer into the nozzle using the pumping fluid path.
Thereafter, the scanning arm operates by two methods according to user's selection.
One hand, in the case that a user wishes to analyze a wafer using an atomic absorption spectroscopy, the scanning arm rotates to move toward a sampling cup tray so that all the pollutant samples which have been used for scanning the wafer are discharged into a sampling cup. If the pollutant samples which have been used for scanning the wafer have been completely discharged into the sampling cup, the scanning arm rotates again so that the nozzle is positioned at the upper portion of the nozzle bottle. Then, the nozzle which has been inserted into the scanning arm is seceded from the scanning arm using a nozzle secession unit which is installed in the scanning device, so as to be distant from the nozzle bottle.
Thereafter, the wafer is transferred to the unloader unit by the transfer unit, and simultaneously unloaded to the outside. As a result, the pollutants collection process is ended.
On the other hand, in the case that a user wishes to analyze a wafer by a total reflection fluorescence X-ray analysis, the scanning arm discharges the pollutant samples which have been used for scanning the wafer to the center of the wafer surface slowly again, and rotates again to make the nozzle positioned at the upper portion of the nozzle bottle. Then, the nozzle which has been inserted into the scanning arm is seceded from the scanning arm using a nozzle secession unit which is installed in the scanning arm so as to be distant from the nozzle bottle. Then, the wafer is transferred to a heating plate in a drying unit, and then dried, to then be transferred to the unloader unit. As a result, the pollutants collection process is ended.
A conventional scan stage which has been known as being used in a process of scanning and collecting pollutants for a semiconductor wafer pollutant measurement apparatus maintains nothing but a loaded state of a wafer, and has only a structure of making both side surfaces of a rotating plate contact a rotating roller to then rotate. Further, whenever a wafer is made to move, an end effector of a robot arm is inserted for itself into the bottom of the wafer so that the wafer is loaded, to thus cause an unstable factor.